Her Discovery
by casness
Summary: Erica discovers who Derek's mate is and learns more about being pack. Derek/Stiles *Now complete*
1. The discovery

_Author's Note: Unbeta'd. First time writing Teen Wolf. This was actually requested by someone on tumblr when I was browsing the sterek tag and I'm not sure who but nonetheless I hope you all like it._

_Disclaimer: Teen Wolf is property of MTV._

Erica enters the warehouse quietly, hoping catch Derek unaware. She hesitates slightly as she remembers his words after the kiss. Shaking her head, she continues down the stairs and towards the train car slowly, making little noise.

She lifts her head up as she hears voices and hides quickly behind a nearby pillar. She hears footsteps from the other entrance and leans against the pillar, slowing down her heart all the while hoping that Derek doesn't notice.

She peeks out and sees Derek leading Stiles to the train car. He has his arms wrapped around Stiles' waist and is nuzzling Stiles' neck.

"Derek," moans Stiles, turning around and leaning up to kiss him.

Derek smiles into the kiss and Erica can see that it's even more intense than the one that she shared with him. He picks up Stiles, causing the other to wrap his legs around Derek's waist.

Derek breaks the kiss and looks up at the train car before striding towards a nearby pillar and leaning Stiles against it.

Erica gulps and watches as Stiles grasps at Derek's shoulders while moaning loudly.

She turns away and leans back against the pillar. She didn't except Derek to be with Stiles or that he would reject her advances. He was different when he turned her but now she could see that it was an act. Stiles is the one he wants.

She peeks out again and watches as Derek grinds against Stiles. He captures Stiles' lips in a bruising kiss then nuzzles the side of his neck.

She knows that he's scent marking him, it's what she wants to do. Erica leans back against the pillar and proceeds to slide down to sit. She keeps her heartbeat steady and silently prays that they either get into the train car or stop making out soon.

After what seemed like an hour, Erica hears Stiles say, "Not here."

She peeks out and sees Stiles push Derek away and grabs his hand before walking to the train car. Derek pulls Stiles closer and briefly kisses him before nudging him to the train car. They both watch Stiles enter the train car and Erica lets out the breath she didn't realize she was holding.

Derek turns and before she can hide behind the pillar, he sees her. "This is the last time that you do this. Leave, now," he said with a serious tone.

She scrambles up and hears him growl as she tries to walk towards him. She hesitates then turns around and exits the warehouse, leaving the two lovers alone. Outside, she looks up and smiles as thinks about going to the school on Monday. It'll give her a chance to tease Stiles about what she saw today.


	2. Alphas and Mates

_Author's Note: Unbeta'd again. Thank you everyone for the kudos and the reviews. Hope you like this chapter._

_Disclaimer: Teen Wolf belongs to MTV._

_Chapter Summary: Erica talks to Stiles then goes to talk to Derek._

* * *

The next morning, Erica catches a ride with Boyd, who was ordered by Derek to pick up Erica and Isaac on his way to school. Erica tries not to think too much into it but can't help but wonder if this is Derek's way of avoiding her. She doesn't tell the two of them about what she saw yesterday. If Stiles gives her problems, then she'll ask for help.

She waits until lunch and corners Stiles in one of the empty classrooms. She doesn't say anything at first, just looks at him and smell Derek's scent all over him. He manages to meet her gaze and again doesn't look at her body like the rest of the guys at the school.

"How do you know Derek?" she questions, leaning against one of the desks. She keeps herself between the door and Stiles, preventing him from leaving.

"Are you going to hit me again? 'Cause we know how well that worked out for you the first time." He shifts from one foot to the other. He puts his backpack down on a nearby desk.

Erica growls at him and lifts up her arm, her claws already out fueled by her rage.

"Hey! Calm down or did you forget that the principal is a hunter, who would like nothing more than the kill any werewolf?" says Stiles, backing away from her.

She puts her hand down and takes a couple of deep breaths. Derek had told them about Gerard Argent a week ago. _Stay out of sight, don't cause trouble_ were the words her Alpha used. "How do you know Derek?" she repeats her question when she's calmed down.

"Scott and I helped him out. We killed the previous Alpha together," answers Stiles.

"The one that bite Lydia," Erica says.

Stiles nods.

"That doesn't explain why you're with him. Why he would chose you over…."

"Over you?" finishes Stiles. "I'm his mate, Erica."

Erica gasps as she now realizes why Derek reacted the way he did. Her wolf whines in a need to apologize to the Alpha's mate, a need to make amends for her behavior. She backs away from Stiles. "You're not even in our pack!"

"Erica…." Stiles starts to say but stops when the bell, for the end of the period, rings.

Erica feels her wolf whine louder, clawing at her wanting to be free and submit to the Alpha's mate. She staggers backwards, yanks the door open and runs out of the classroom.

She ends up running from the school to the warehouse, the unconscious need to be close to the Alpha in times of distress leads her there. She walks in slowly and is startled when she sees Derek sitting on the step in front of the opening of the train car.

"Alpha," she whispers as she slowly walks forward.

"Erica," says Derek. He motions her to come closer.

Erica wants to him but manages to restrain herself to a brisk walk. She sits down next to him, nervous and unsure of her discovery.

"I told you to stay away from Stiles. Why did he just text me and told me that you both talked," Derek prompts her to talk.

"He said that he was your mate. You need an Alpha female, he isn't even a werewo-" She stops and shrinks away when Derek growls at her.

"Stiles has always been my mate, even before I was an Alpha. You will not question that!" Derek stands and looks at her. His eyes glowing red.

"He's not even pack!" Erica manages to shout before her wolf's need to submit to the Alpha overpowers her and she cowers away from him.

"You don't decide who is pack!"

Erica whines and curls up on the floor. Her wolf hopes that the submissive pose will appease the Alpha.

After a couple of minutes, Derek's changes subside. His eyes turn back to their natural color and he sighs. He holds out a hand to Erica, who slowly comes closer before hugging him.

"I'm sorry, Alpha," she whispers. Her wolf's need for reassurance surfaces and she tightens her grip.

Derek pets her hair and whispers reassurances as she starts to cry.

After a while, her tears stop and she wipes her eyes with the sleeve of her shirt. She finally loosens her grip on his shirt and sits back. Erica waits until Derek sits down before saying, "He should be pack though."

Derek lifts up her chin to look her in the eyes. A few seconds pass with him looking into her eyes before he starts to talk. "With the Kanima and Argents around, it's too dangerous for Stiles to be part of my pack. After we deal with everything, I'll formally claim him. For now though, stay away from him."

Erica nods. She isn't sure what he found in her expression but she's grateful for Derek's explanation. It eases the confusion that both she and her wolf feel. She still feels a bit angry for not being the Alpha female but at least now she feels balanced, more at ease with her discovery.

She thanks Derek and promises to show up for training later on in the day before leaving the warehouse. She may not be the Alpha's mate and she may not _yet_ like his mate but she makes a promise to herself to watch out for Stiles and protect him if need be. He may not be pack but he was still Derek's mate and their second Alpha.


	3. Teasing

_Author's Note: Thank you for the follows, favorites and comments. This chapter has spoilers for 2x07 "Restraint". I hope that you enjoy it._  
_Disclaimer: Teen Wolf belongs to MTV._

* * *

Erica wakes up sore. She glances at her arm and notices that the scratch from the Kanima is bandaged up. _Stiles_, she thinks. She shifts on the cot and inhales, taking in the smells around her. The warehouse has different smells but in the train car, where she lays, the scents of Scott, Boyd, Isaac, and Derek with Stiles linger but mostly she smells Stiles' scent. The scent that calms her wolf.

"Hey, you're awake," says Stiles, leaning over to check on her. He touches her forehead and adjusts the blanket around her body.

"How long was I out?" she asks. Her voice is hoarse and she feels tired.

"A day," answers Stiles. He helps her sit up and holds a bottle of water for her to drink.

She takes a sip to begin with then drinks most of it from thirst. She says, "Thank you" and watches as he puts the bottle on a stand near the cot. Sitting up makes it better for her to glance around. She looks out at the train car window and sees Derek with Scott sitting on crates. From there, she finally looks at Stiles and takes in his appearance. The dark hickey on his neck, the bite marks that _Derek's_shirt doesn't cover. At least he's wearing his own jeans, she thinks as she laughs.

"Yeah, laugh it up. We were worried!" scolds Stiles. He sits on a chair a couple of feet from the bed. "You collapsed while we were trying to get the venom out of you. Derek said you needed time to heal."

"So, why are you here?" She folds her arms in her lap.

"We're pack. Pack takes care of each other."

She blushes. "Thanks...pack mom," she says with a smile. Her wolf has for a while accepted Stiles' position of Alpha's mate, of the caregiver the pack. It's only now that Erica starts to realize what the Alpha's mate is and does for the pack.

"Pack mom? Yeah...umm...there's something that we have to discuss," says Stiles. He reaches out to touch the hickey but pulls his hand back before touching it.

"You mated?" guesses Erica.

"We were already mated! No, Derek and the rest of the pack accepted me as Alpha's mate." Stiles blushes.

"So you need my acceptance?" Erica teases.

Stiles nods and looks out to the warehouse. When Derek meets his gaze, he blushes and ducks his head down.

"I acknowledged you as his mate after talking to Derek. Or is there a ritual that I have to perform? Like do we have to sleep together?" Erica says. Her voice full of acceptance and laughter. She hears a loud growl from Derek and ducks her head in submission.

"No! No sex with anyone. Except for Derek. Only Derek," says Stiles. He gets up and hugs her. "Thank you."

She nods and hesitantly accepts the hug. "You do make a good Batman, Stiles."

"Thanks. You make a pretty good Catwoman." He lets go of her and sits on the edge of the cot.

"Since you're part of the pack, I guess we should get used to seeing you in Derek's clothes."

"Hey, my shirt got dirty, that's all," explains Stiles.

"And the hickey and bite marks?" teases Erica.

Stiles blushes and gets up from the cot. He walks out of the train car and into the warehouse, where he shouts, "She's fine!"

Erica ends up laying back down on the cot, laughing. _This will be fun_, she thinks as she imagines teasing Stiles in the future.


	4. Guarding

_Author's Note: I just want to say thank you again for all of the kudos, support and comments. I'm glad that everyone is enjoying this. Sorry for the long time between chapters. RL and muse is quiet evil and at conflict with one another. Again, this is unbeta'd. Any major problems, please let me know and I'll edit it. :)_

_Disclaimer: I don't own Teen Wolf._

Summary: Takes place after 2x08. Erica watches over Stiles.

* * *

Erica stands across the street from Stiles' house, unintentionally listening to the conversation between Stiles and his father.

"So, what happens now?" she hears Stiles ask, his voice filled with sorrow.

"Now? You get to bed. You have school in the morning," the sheriff replies.

Erica looks down, her eyes wet from unshed tears. She's heard the entire conversation and knows that it is the pack's fault, the secrets that Stiles and the rest of them are keeping that created the rift between father and son.

She hears Stiles head upstairs and enter his room. He collapses on his bed and the increase in his heartbeat indicates to her that he's trying to stop himself from crying but fails. Erica sits on cold ground and hugs her knees to her chest. Leaning against a tree, she listens to her Alpha's mate cry.

She's not sure how they will recover from this. Derek had taken Scott to Dr. Deaton's with Isaac, the other _Alpha_ had been exposed to a vapor form of wolfs bane. On one hand, Erica's glad that it was Scott not Derek or Isaac but she knew that was selfish. Scott and Stiles have become pack, Stiles more so since she found out that he and Derek were mates.

She didn't hear Derek approach until he sits down next to her. He put an arm around her and pulls her close. He hold her in the dark of the night across from his mate's house, comforting her as an alpha should.

After some time, she pulls away from him and stands. "Thank you."

Derek stands up as well and he looks at her for a moment before saying, "Go home. Isaac is watching over Scott tonight at Deaton's."

She nods in response and turns to walk away but before she can leave, Derek grabs her arm. "Be careful. Don't take any chances, Erica. We have hunters and the kanima after us."

She nods again and when Derek lets go of her arm, she walks away. After only a few feet away from Derek, she turns around and sees Derek walking toward Stiles' house then climb up to and through his window.

She breathes in deeply, calming herself and tries to focus on one sense. She hears the chirping of the crickets, the dog barking the next house over, the sheriff snoring and finally narrows in on Derek's movements.

She hears him move to Stiles' bed, the blankets shifting as he sits down near Stiles and gathers him in his arms. Closing her eyes, she listens in more attentively to the words exchanged between the two lovers.

"He's no longer sheriff," Stiles whispers. His heartbeat skips and Erica assumes that it was from something that Derek did.

She doesn't hear Derek's reply instead she knows that it was comforting because Stiles' heartbeat was calmer. She hopes to hear more but knows now, after many lessons, that Stiles has fallen asleep. So she concentrates on Derek and hears the honest whisper of "I love you".

Erica opens her eyes and finds herself assaulted by different sounds from her surrounding, concentrating too much on one can do that. She smiles slightly before turning back around and running home. Her desire to guard Stiles is still there but she knows that no one can protect him better than Derek, his own mate.


	5. Advice

_Author's Note: Teen Wolf doesn't belong to me. Thank you for everyone who commented, followed, gave kudos and favorited this. There are two more chapters after this one. This chapter is 2x09 and 2x10. Unbeta'd. _

* * *

"Why do you have all of this stuff?" asks Erica. She runs a hand over the boxed up flat screen tv then toys with the bracelets on Stiles' nightstand, unintentionally marking them with her scent.

"It's for Lydia," answers Stiles. When Erica gives him a look, he continues, "Not all of it! I'm still trying to figure out what to give her."

"Why are you giving her a present?" Erica asks as she sits on Stiles' bed. The faint smell of Derek lingering on his sheets makes her lean down and lay on his bed. Since the turning, Derek's scent - no the _Alpha's _scent calms her.

"She's still my friend, Erica. Scott and I are going to her party tomorrow while you're..." he waves a hand toward her.

"Having that time of the month?" Erica finishes with a smirk.

"At Derek's. I really didn't want to know about that." He sits on the computer chair and turns it around to face her. "Aren't you supposed to be there now?"

"Later. So what did Derek say about all this?" She motions to the various types of gifts that Stiles bought.

"He's being a sour wolf about it." He looks out the window briefly before turning to face Erica again.

Erica looks around and notices a box in the other corner. She glances at Stiles, who is now busy on his computer before standing up and walking over to the box. When she looks inside she smiles and exclaims, "This. Stiles, you have to give her this. I've always wanted one. Trust me, she'll like it."

Stiles looks at Erica as she puts the box on his bed and starts to wrap up the box. "Hey!" he shouts as he tries to shoo Erica away from the box but fails. "Are you even sure that she'll like it?"

"Stiles, she'll love it. It's from you," Erica reassures him. When she's done wrapping up the present, she sets it down in the corner by his door. She sits next to Stiles who's now on the bed and leans her head against his shoulder. "Can I ask you something?"

Stiles nods and wraps an arm around her.

"Why doesn't Scott smell like pack?" asks Erica.

"What do you mean?"

"I feel like he's hiding something. He doesn't feel like pack. Isaac says he does but he doesn't smell like pack." Erica lifts up her head as she hears a distant howling of her Alpha calling the pack to the warehouse. Before she leaves, she turns to Stiles. "Derek's calling. Be careful at the party. Jackson and his master are still out there."

Stiles sighs as Erica goes out the window.

Later that night before Derek puts the head restraint on her, she voices her concerns, "Stiles is at Lydia's with Scott."

"I know," he replies. His eyes glow red for a brief second before returning to their normal color.

"Scott doesn't smell like pack."

"Erica," Derek growls, "I'll take care of it." He puts the head restraint on her and she screams as her wolf howls inside of her.

Her wolf howls at the full moon and the desire to be free and run over powers her. The last thought that runs through her mind is for Stiles to be safe tonight from both the Kanima and Scott.


	6. Lost packmate

_Author's Note: Thank you everyone that's reviewed, gave kudos, followed and bookmarked. Teen Wolf does not belong to me. This takes place during episode 11. The next chapter is the final chapter. :)_

* * *

"Hi," says Erica greeting Stiles. She sits on the bench next to him and leans her head on his shoulder, joining Stiles in watching as other students hurry to class.

Stiles glances at her and attempts to smile briefly.

"I heard what happened at Lydia's and later at the station," she says. Her wolf whines, wanting to comfort the Alpha's mate.

"I already talked to the counselor about it," replies Stiles.

"Talked to her about all the wolfiness?" snorts Erica.

"Wolfiness?"

"It seems like a word you would use," Erica replies, leaning away from him and sitting up.

"You were right, by the way." Seeing Erica looking at him in confusion, Stiles continued, "Scott isn't pack. Derek told me about what happened about Scott working with the hunters."

A whine escapes her because she could stop it. She knows what it means for Stiles to say that, especially about a packmate, especially one that he's known most of his life. Because that's what Scott and Stiles were - their own pack, before this, before Scott turned into a werewolf and got Stiles involved. "Are you-"

"Don't even ask that. I'm...I'll be okay. I just need to get..." His cell phone vibrating stops him mid sentence. Stiles takes it out from his pocket and reads the text message then puts it away.

Erica can smell the sadness on him and her wolf howls in grief. She lost a packmate today and an ally. "What about his mom?"

"She's dealing with it. It'll take some time for her to get used to it," answers Stiles.

"And your dad?"

"He doesn't know anything and he won't. It's too dangerous," answers Stiles, sternly. He stands up and looks at her.

Erica put her hands up. "He won't hear it from me or any of the pack," she promises.

Stiles nods and picks up his lacrosse equipment. "I have practice. I'll see you later," he says.

"Sure," she smiles slightly. She looks at her feet and sighs. _Maybe I'll be able to talk to him after_, she thinks as she resists the urge to run after Stiles and tell him.

It was only later, much later when Erica is running for her life that she regrets not telling Stiles about what she and Boyd have decided. Stiles was her last hope for a reason to stay. Yes, he's the alpha's mate but he was hers before he was Derek's. She knew him longer, had a crush on him. She had wanted him to be her reason to stay. Her anger at Derek, at the Argent's cheap trick fuels her to run further.

Later when she and Boyd are caught, Erica prays for the first time that Derek doesn't tell Stiles about her leaving, that Stiles won't come to rescue her.


	7. Running

_Author's Note: This takes place at the Teen Wolf Season 2 finale. Thank you everyone for taking the journey with Erica. I hope that you enjoyed it. :) _

* * *

Erica snarls at Chris Argent when the man releases chains holding her and Boyd. She feels Boyd holding her back, whispering that Chris released them and he's on their side but Erica pays no heed to his words. There is only one thought that runs through her mind, he hurt Stiles, Alpha's mate.

Chris backs away and lets Boyd calm her down. "I'm going to get Gerard. Come with me if you want," he states before climbing up the stairs.

Erica rages and for the first time since her decision to leave, her wolf is torn. She looks up at Boyd. "What do we do?"

"Leave. We left Derek's pack. Alpha won't take us back now. There are other packs," he answers.

Erica nods. She stands in the middle of the room and takes in Stiles' scent, in hopes that it would calm her. Her wolf howls in response, the pain of being unable to protect the mate has angered it and Erica knows that unless she gains control, she'll come back to Derek. Derek, her first Alpha who gave her no reason to stay.

Erica kneels and runs her hand across the small drop of blood on the floor. She looks up at Boyd and notices the anger in his eyes. "Derek couldn't protect Stiles," she states in anger.

Boyd nods.

"We need to find a new Alpha, a new home," she voices her thoughts. Seeing Boyd nod again, she smiles. "Let's run, there's a pack out there. I know there is."

She hurries upstairs with Boyd following her and heads outside. Giving him a quick glance, she starts to run into the forest. This time it's the need to protect Stiles that fuels her to run and find this new pack.


End file.
